Hello and thank you for the question.

Apologies for the delay in answering.  As I am sure you can imagine we are getting many, many questions right now. 

To prepare your lawn for seeding, you should address the Japanese beetle grubs before you start the seeding process. Since grubs are most active in the middle to late summer, it's advisable to control them at this time. You can start by scouting for grubs in your lawn by cutting a few square-foot samples of the turf, examining the soil for grubs, and replacing the sod after.  I always recommend doing a soil test as well to amend soil conditions for best results when planting seed or sod.  Here is a link: https://extension.umn.edu/managing-soil-and-nutrients/soil-testing-lawns-and-gardens

If you find an average of three to five grubs per square foot, treatment is recommended. It's important to water the lawn thoroughly before applying any insecticide to bring the grubs closer to the soil surface. After application, water the area again to help the chemical reach the grubs.

For controlling grubs, you can use a long-lasting insecticide like imidacloprid or chlorantraniliprole, which are effective against grubs. Ensure that you follow the label directions and use the products only on the recommended plants.

As for the type of grass seed, it would be best to choose a seed that is suitable for your soil type and the amount of sunlight your yard receives. For areas with full sun to partial shade, you could consider grass varieties like tall fescue, Kentucky bluegrass, or perennial ryegrass. It's also important to ensure that your soil is prepared properly for seeding, which may include removing any debris, improving the soil structure, and ensuring proper soil moisture.  

https://extension.umn.edu/yard-and-garden-insects/japanese-beetles

https://www.aphis.usda.gov/sites/default/files/JBhandbook.pdf

I hope this is helpful.  Please reach back if you have further questions.